Drilling fluids based on polymer complexes

ABSTRACT

An oil-based drilling mud which comprises an organic liquid substantially immiscible in water; about 1 to about 10 parts by weight of water per 100 parts by weight of the organic liquid; about 20 to about 50 lb./bbl. of at least one emulsifier; weighting material necessary to achieve the desired density; and about 0.25 to about 4.0 lb/bbl. of a hydrocarbon soluble polymeric complex formed from a water insoluble anionic polymer and a cationic polymer.

This application is a continuation-in-part of U.S. Ser. No. 079,130,filed July 29, 1987, now abandoned, which in turn is acontinuation-in-part of U.S. Ser. No. 894,561, filed on Aug. 8, 1986,now abandoned, which in turn is a Continuation of U.S. Ser. No. 651,906,filed Sept. 19, 1984, now abandoned.

FIELD OF INVENTION

The present invention relates to polymeric complexes which function asviscosification agents when added to oil-based drilling muds which arethe fluids used to maintain pressure, cool drill bits and lift cuttingsfrom the holes in the drilling operation for oil and gas wells. Thepolymeric complex is formed from the interaction of a cationic and ananionic polymer.

The drilling muds formed from these polymeric complexes exhibit improvedlow and high temperature rheological properties as compared to drillingmuds formed from powders of sulfonated thermoplastic polymers.

BACKGROUND OF THE INVENTION

In the field of drilling in the exploration for oil and gas, animportant component is that of the formulation of drilling muds.Drilling muds are the fluids which are used to maintain pressure, cooldrill bits, and lift cuttings from the holes and vary in compositionover a wide spectrum. Generally, drilling muds are based on aqueousformulations or oil-based formulations.

A conventional oil-based drilling mud formulation is comprised ofbasically the following ingredients: oil (generally No. 2 diesel fuel),emulsified agents (alkaline soaps and fatty acids), wetting agents(dodecylbenzene sulfonate), water, barite or barium sulfate, (weightingagent), asbestos (employed as viscosification agent) and/or, aminetreated clays (also as viscosification agent).

The above combination of ingredients is generally formulated to possessvarious weights based primarily on amount of barite added. For example,a typical drilling mud can vary in specific gravity from a range ofabout 7 pounds per gallon up to 17 pounds per gallon or even greater.This variation in specific gravity is primarily controlled by the amountof barite added. The above formulations perform adequately in a numberof applications, primarily those where the use of oil-based drillingmuds is dictated by the lack of stability of the formation in whichdrilling is taking place. For example, in various types of shaleformation, the use of conventional water-based muds can result in adeterioration and collapse of the shale formation. The use of theoil-based formulations circumvents this problem. However, it is observedthat the current oil-based drilling muds have some significantdisadvantages. One disadvantage is that the incorporation of asbestos orasbestos fines can incur significant health problems, both during themud formulation and potentially during the subsequent use of suchformulations. Therefore, it is desirable to eliminate the use ofasbestos completely in such drilling muds. On the other hand, the use ofsubstitutes for asbestos in this application has; heretofore, not beenparticularly successful in that the resulting viscosification agentsmust maintain adequate viscosities under the drilling conditions whichcan involve high temperature and high shear conditions.

There has been a substantial need for a drilling fluid which wouldexhibit good performance at high temperature in water sensitiveformations. Past experience has shown that oil-based drilling fluids canprovide good performance in water sensitive formations, and the state ofthe art systems can perform well up to about 350° F. Typically, in suchformations, the failure of the viscosities in current muds iscircumvented by the addition of more viscosifier during the circulationof the drilling mud. While this solution is adequate at moderatetemperatures, when much higher temperatures are encountered (example:geothermal wells or natural gas wells), the degradation of theviscosifier can be so rapid that the additional costs for a viscosifiercan be uneconomical. There is a need; therefore, for drilling fluidswhich can maintain their viscosity and gel strength at temperatures upto and exceeding 400° F. These needs are not adequately met by thecurrent drilling fluids, even with the oil-based drilling muds oftenemployed.

This invention describes an approach to viscosification of oil-baseddrilling muds which permits the substitution of a polymeric complex forasbestos fines and amine clays. The resulting polymer-modified drillingmuds display improved low and high temperature rheological propertieswhich include improved gel strength at up to temperatures or 400° F. andhigher, based on tests conducted for 16 hours at such temperatures.

It has also been shown that sulfonated EPDM is very effective as aviscosifier for oil-based drilling muds, as described in U.S. Ser. No.292,235 entitled, "Drilling Mud Viscosification Agents Based onSulfonated Ionomers." We have found that sulfonated EPDM provides goodviscosification at temperatures of about 300° F. and below whenformulated in a mud based on fresh water, but loses its effectiveness athigher temperatures.

In U.S. Ser. No. 292,233, a high temperature drilling mud was formulatedby the incorporation of a powdered, sulfonated polystyrene directly intothe drilling mud. The instant application differs from U.S. Ser. No.292,233 in that a latex of the sulfonated polystyrene is used toformulate the drilling mud. Quite unexpectedly, the use of the instantpolymer complexes in drilling mud rather than the sulfonatedpolystyrenes, results in a drilling mud having improved low temperaturerheological properties.

The instant invention will describe polymeric complexes which willprovide oil-based drilling muds having provided improved, excellent gelstrength at low and high temperatures and may be effective at evenhigher temperatures.

A second facet of the instant invention relates to the use of thesematerials in formulations which employ high concentrations of salt inthe aqueous phase. The polymer complexes which are the preferredembodiment of this invention, lose some of their efficacy in salt water.It has been found that the combination of a suitable non-ionicemulsifier with the polymer complexes gives formulations which areeffective with salt water. Therefore, these systems give formulationswhich perform well at low temperatures and in the presence of salt waterphases, which is a highly desired objective in the drilling fluidsindustry.

SUMMARY OF THE INVENTION

The present invention relates to polymer complexes which function asviscosification agents when added to oil-based drilling muds which, arethe fluids used to maintain pressure, cool drill bits and lift cuttingsfrom the holes in the drilling operation for oil and gas wells.

The drilling muds formed from these polymer complexes exhibit improvedlow and high temperature rheological properties as compared to drillingmuds formed from powders of sulfonated thermoplastic polymers.

GENERAL DESCRIPTION OF THE INVENTION

The present invention describes a new class of viscosification agentsfor oil-based drilling muds which are used during operation of gas andoil wells, wherein these viscosification agents are polymer complexes.The oil-based drilling muds of the instant invention minimally comprise,but can also include other additives; an organic liquid such as an oil,fresh water or salt water, an emulsifier, a wetting agent, a weightingmaterial and a polymer complex. In 9general, the oil-based drilling mudhas a specific gravity of about 7 pounds per gallon to about 20 poundsper gallon, more preferably about 10 to about 16, and most preferablyabout 12 to about 16. A typical oil-based drilling mud, as envisioned bythe instant invention, comprises: an oil; about 1 to about 10 parts byweight of water per 100 parts by weight of the oil, more preferablyabout 3 to about 5; and 20 to about 50 lb/bbl. of an emulsifier and/orsupplementary emulsifier; about 1/2 to about 5 lb/bbl. of a wettingagent; and a sufficient amount of weighting material (barium sulfate orbarite) necessary to give the desired mud density which comprises lessthan bout 800 lb/bbl. of barium sulfate, more preferably about 5 toabout 750, and most preferably about 10 to about 70; and about 0.1 toabout 50 lb/bbl. of a polymer complex.

The oil employed in the oil-based drilling mud is generally a No. 2diesel fuel, but it can be other commercially available hydrocarbonsolvents such as kerosene, fuel oils or selected crude. If crudes areused, they should be weathered and must be free of emulsion breakers.

Typical, but non-limiting examples of suitable emulsifiers which can bereadily employed are magnesium or calcium soaps of fatty acids.

Typical, but non-limiting examples of a suitable wetting agent which canbe readily employed is an alkylaryl sulfonate.

Typical, but non-limiting examples of a weighting material which can bereadily employed is barite or a barium sulfate which may optionally besurface-treated with other cations, such as calcium.

In general, the water insoluble interpolymer complex comprises a mixtureof a polymer comprised of anionic groups such as metal sulfonates and apolymer containing basic amine groups such as pyridine or other aminespecies. The anionic polymer contains from about 10 to about 200 meq.pendant ionomeric groups per 100 grams of polymer, more preferably from10 to 100 meq. pendant ionomeric groups. The ionic groups may beconveniently selected from the groups consisting of carboxylate,phosphonate, and sulfonate, preferably sulfonate groups. In mostinstances, the anionic polymers utilized in the instant invention areneutralized with the basic materials selected from Groups IA, IIA, IVA,VIA, VIIA, VIIIA, IB and IIB of the Periodic Table of Elements and lead,aluminum, tin and antimony, as well as ammonium and amine counterions.Anionic polymers which are subject to the process of the instantinvention are illimitable and include both plastic and elastic polymers.Specific polymers include sulfonated polystyrene, sulfonated t-butulstyrene, sulfonated para-methylstyrene, sulfonated ethylene copolymers,sulfonated propylene copolymers, sulfonated styrene/acrylonitrilecopolymers, sulfonated styrene/alkyl methacrylate copolymers, alkylacrylate copolymers, maleic copolymers, alkyl malcate copolymers,sulfonated block copolymers of styrene/ethylene oxide, acrylic acidcopolymers with styrene, sulfonated polyisobutylene, sulfonatedethylenepropylene terpolymers, sulfonated polyisoprene, and sulfonatedelastomers and their copolymers. The preferred polymers of the instantinvention are ethylenepropylene terpolymers and polystyrene, wherein theethylenepropylene terpolymer is most preferred.

Neutralization of the anionic polymers with appropriate metalhydroxides, metal acetates, metal oxides, or ammonium hydroxide etc.,can be conducted by means well-known in the art. For example, thesulfonation process as with butyl rubber containing a small 0.3 to 1.0mole percent unsaturation can be conducted in a suitable solvent such astoluene, with acetyl sulfate as the sulfonated agent, such as describedin U.S. Pat. No. 3,836,511. The resulting sulfonic acid derivative canthen be neturalized with a number of different neutralization agentssuch as a sodium phenolate and similar metal salts. The amounts of suchneutralization agents employed will normally be equal stoichiometricallyto the amount of free acid in the polymer plus any unreacted reagentwhich is still present. It is preferred that the amount of neutralizingagent be equal to the molar amount of sulfonating agent originallyemployed plus 10 percent more to insure full neutralization. The use ofmore of such neturalization agent is not critical. Sufficientneutralization agent is necessary to effect at least 50 percentneutralization of the sulfonic acid groups present in the polymer,preferably at least 90 percent, and most preferably essentially completeneutralization of such acid groups should be effected.

The degree of neutralization of said anionic groups may vary from 0(free acid form) to greater than 100 mole percent. With the utilizationof neutralized anionic in this instant invention, it is preferred thatthe degree of neutralization be substantially complete, that is with nosubstantial free acid present and without substantial excess of the baseother than that needed to insure neutralization. The neturalized anionicpolymers possess greater thermal stability compared to its acid form.Thus, it is clear that the polymers which are normally utilized in theinstant invention comprise substantially neutralized pendant groups, andin fact, an excess of the neutralizing material may be utilized withoutdefeating the objects of the instant invention.

The anionic polymers of the instant invention may vary in number averagemolecular weight as measured by GPC from 1,000 to 10,000,000 preferablyfrom 5,000 to 50,000, most preferably from 10,000 to 200,000. Thesepolymers may be prepared by methods known in the art, for example, seeU.S. Pat. No. 3,836,511, hereby incorporated by reference.

The water insoluble, ionomeric polymers may be incorporated into asolvent system of an organic liquid and a polar cosolvent to form afirst solution at a level of from 0.2 to 10 weight percent and morepreferably from about 0.5 to 10 weight percent, based on the organicliquid and the polar cosolvent.

Specific examples of preferred anionic polymers which are useful in theinstant invention include sulfonated polystyrene, sulfonatedpoly-t-butyl styrene, sulfonated para-methylstyrene sulfonatedpolyethylene (substantially noncrystalline), and sulfonated ethylenecopolymers, sulfonated polypropylene (substantially noncrystalline), andsulfonated polypropylene copolymers, sulfonated styrenealkylmethacrylate copolymers (styrene)-acrylic acid copolymers, alkylacrylate copolymers maleic and maleic acid ester copolymers, sulfonatedpolyisobutylene, sulfonated ethylenepropylene terpolymers, sulfonatedpolyisoprene, sulfonated polyvinyl toluene and sulfonated polyvinyltoluene copolymers.

The anionic polymers of the instant invention may be prepared prior toincorporation into the organic solvent, or by neutralization of the acidfrom in-situ. For example, preferably the acid derivative is neutralizedimmediately after preparation. For example, if the sulfonation ofpolystyrene is conducted in solution, then the neutralization of thatacid derivative can be conducted immediately following the sulfonationprocedure. The neutralized anionic polymer may then be isolated by meanswell-known to those skilled in the art, i.e., coagulation, steamstripping, or solvent evaporation, because the neturalized polymer hassufficient thermal stability to be dried for employment at a later timein the process of the instant invention. It is well-known that theunneutralized sulfonic acid derivatives do not possess good thermalstability and the above operations avoid that problem.

It is also possible to neutralize the acid form of these anionicpolymers in situ; however, this is not a preferred operation, since insitu neutralization requires preparation of the sulfonic acid in theorganic liquid which is to be subjected to the instant process, or theacid form of the anionic polymer must be dissolved in said organicliquid. The latter approach may involve handling of an acid form of ananionic polymer which has limited thermal stability. Therefore, it isquite apparent that the prepartion and isolation of a neutralizedanionic polymer affords the maximum latitude in formulation, lessproblems in handling polymers of limited thermal stability and maximumcontrol over the final mixture of anionic polymer, polar cosolvent andorganic liquid.

We have surprisingly found that a very important factor in determiningthe strength of the interaction between the amine-containing polymer andthe sulfonate-containing polymer is the nature of the counterion. Thereare, broadly speaking, three major classes of such counterions. Thefirst class, which are less preferred, are those metals of Group I andGroup IIA, which include Li, Na, K, etc., Be, Mg, Ca, etc. We have foundthat these species do not interact as strongly with amine groups as themore preferred species described below. Those metals are commonlydefined as members of the transition elements (see chemical text:"Chemical Principles and Properties," by M. J. Sienko and R. A. Plane,McGraw Hill Book Co., 1974, page 19). These metal cations are bestexemplified by zinc and interact strongly with pyridine and similaramines. As a consequence, a zinc neutralized sulfonated polymerintereacts much more strongly with a styrene/vinyl pyridine copolymerthan does a magnesium or sodium neutralized system. It is for thisreason that the transition elements are preferred with zinc, copper,iron, nickel and cobalt being especially preferred. We also includeantimony and lead as suitable cations.

A third species which is preferred is the free acid of the sulfonatedpolymer, which will also interact with amine-containing polymers. Inthis latter case, it is clear that the interaction is a classicacid-base interaction, while with the transition metals, a truecoordination complex is created, which is due to the donation of theelectron pair of the nitrogen element. This distinction is a veryimportant one and sets these complexes apart from classic acid-baseinteractions. The surprising observation is that such coordinationcomplexes can form in such extreme dilution insofar as interactinggroups are concerned, and that they are apparently formed so far removedfrom their expected stoichiometry, (based on small molecule analogs).

The organic liquids, which may be utilized in the instant invention, areselected with relation to the anionic and cationic polymer andvice-versa. The organic liquid is selected from the group consisting ofparaffinic, napthenic and aromatic hydrocarbons, cyclic aliphaticethers, aliphatic ethers, or organic aliphatic esters and mixturesthereof.

The amine containing polymers employed in the instant invention arepolymers containing about 0.1 to about 25 weight percent amine groups,more preferably about 0.5 to about 20, and most preferably about 1 toabout 15. An especially preferred cationic polymer is vinyl pyridine.The molecular weight of the amine polymers, as measured by gelchromatography permeation, is about 10,000 to about 10,000,000 morepreferably about 200,000 to about 5,000,000 and most preferably 50,000to about 3,000,000. The cationic polymer is dissovled in a solventsystem identical to the solvent system used to form the first solutionof the anionic polymer. The second solution of the cationic polymersolvent and polar cosolvent contains about 0.1 to about 25 weightpercent of cationic polymer, more preferably about 0.5 to about 15, mostpreferably about 0.5 to about 10.

The first solution of the anionic polymer and the second solution of theamine containing polymer are mixed together to form the interpolymercomplex which is the association of the anionic and cationic polymersthrough the formation of a complex which leads to a network formation.The molar ratio of the anionic/cationic polymers is about 0.1 to about20, more preferably about 0.2 to about 15, and most preferably about 0.4to about 10.

Specific examples of organic liquids to be employed with the varioustypes of polymers are:

    ______________________________________                                        Polymer            Organic Liquid                                             ______________________________________                                        sulfonated polystyrene                                                                           benzene, toluene, ethyl                                                       benzene, methylethyl                                                          ketone, xylene, styrene,                                                      ethylenedichloride, methy-                                                    lene chloride                                              sulfonated poly-t-butyl-                                                                         benzene, toluene, xy-                                      styrene            lene, ethyl benzene                                                           styrene, t-butyl                                                              styrene, aliphatic oils,                                                      aromatic oils, hexane,                                                        heptane, decane, nonane.                                   sulfonated ethylene-                                                                             pentane, aliphatic and                                     propylene terpolymer                                                                             aromatic solvents, oils                                                       such as "Solvent 100                                                          Neutral," "150 Neutral"                                                       and similar oils, benzene                                                     diesel oil, toluene,                                                          xylene, ethyl benzene,                                                        pentane, hexane, heptane,                                                     octane, isooctane, no-                                                        nane, decane aromatic                                                         solvents, ketone sol-                                                         vents.                                                     sulfonated styrene-methyl                                                                        dioxane, halogenated ali-                                  methacrylate copolymer                                                                           phatics, e.g., methylene                                                      chloride, tetrahy-                                                            drofuran.                                                  sulfonated polyisobutylene                                                                       saturated aliphatic hydro-                                                    carbons, diisobutylene,                                                       triisobutylene, aromatic                                                      and alkyl substituted                                                         aromatic hydrocarbons,                                                        chlorinated hydrocarbons,                                                     n-butyl ether, n-amyl,                                                        ether, methyl oleate,                                                         aliphatic oils, oils                                                          predominantly paraffinic                                                      in nature and mixtures                                                        containing napthenic                                                          hydrocarbons. "Solvent                                                        100 Neutral," "Solvent                                                        150 Neutral" and all                                                          related oils, low mole-                                                       cular weight polymeric                                                        oils such as squalene,                                                        white oils and process                                                        oils having 60 percent                                                        or less aromatic                                                              content.                                                   sulfonated polyvinyl toluene                                                                     toluene benzene,                                                              xylene, cyclohexane,                                                          ethyl benzene, styrene,                                                       methylene chloride,                                                           ethylene dichloride.                                       vinyl pyridine with styrene                                                                      benzene, toluene,                                          or t-butyl styrene xylene, ethyl benzene,                                                        styrene, t-butyl                                                              styrene, aliphatic                                                            oils, aromatic oils,                                                          hexane, heptane,                                                              decane, nonane.                                            ______________________________________                                    

The solution of the hydrocarbon soluble complex and organic liquid areadded to the drilling mud formulation by conventional solutiontechniques to form the polymer modified drilling muds of the instantinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following are preferred embodiments of the instant invention.

EXAMPLE 1 Preparation of Styrene-4-Vinyl Pyridine Copolymer

A copolymer of styrene-4-vinylpyridine was prepared via a free radicalemulsion copolymerization process. The preparation was conducted asfollows:

In a suitable, stirred reaction vessel under a nitrogen blanket thefollowing ingredients were charged.

120 ml. distilled water

50 g. styrene

3.2 g. sodium lauryl sulfate

0.1 g. dodecylthiol

0.2 g. potassium persulfate

4.7 g. 4-vinyl pyridine

The polymerization was conducted at 50° C. for 24 hours and theresultant emulsion was fluid and uniform. Three ml. of methanolcontaining 0.1% of hydroquinone was added as an inhibitor and thereaction mixture was precipitated in a large excess of acetone. Theprecipitate was filtered, then suspended in methanol and blended in aWaring blender to finally disperse the coagulated polymer. Thesuspension was filtered and dryed in a vacuum oven at 60° C. for 24hours.

EXAMPLE 2 Preparation of Sulfonated EPDM

The preparation of sulfonated EPDM has been well-described in the patentand published literature for example, see U.S. Pat. No. 4,184,988 or ACSMonograph edited by A. Eisenberg, 1980, p. 4). A zinc sulfonated EPDMwas prepared via those procedures containing 10 meq. of zinc sulfonate,designated TP 398. The resulting polymer was available as a free-flowingcrumb and employed in that form as a blending component in the followingexamples.

EXAMPLE 3 Preparation of Polymer Complex

The polymer complex of sulfonated EPDM and polystyrene-Co-4-vinylpyridine is prepared by charging the required amounts of each polymer toa flask, adding xylene in sufficient quantity to produce the desiredconcentration and stirring at room temperature until a homogeneoussolution is obtained. This generally requires from 2 to 24 hoursdepending on the concentration required.

EXAMPLE 4

The use of the polymer complex as an oil mud viscosifier is shown in itsinclusion in an OIL FAZE MUD SYSTEM (Dresser Magcobar Inc.).Specifically these oil based muds were prepared using conventionallaboratory methods. A typical mud was prepared by mixing 205.82 g. ofNo. 2 diesel oil, 34.76 g. Oil Faze (Magcobar), 1.5 g. SE-11 and 1.5 g.DV33 (Magcobar). To this mixture was added 10 g. of CaCl₂ in 21 ml. ofwater. The mud was weighed with 226.35 g. of Barite and then 4.4 g. ofadditional CaCl₂ was added. The control contained amine-treated clay ata 3 lb/bbl. treat rate. The sodium salt of the sulfonated styrene (1.7mole % sulfonate units) was added at 1 and 2 lb/bbl. treat rates or (1.1and 2.2 grams respectively). The remaining two examples both containpoly styrenevinyl pyridine (6 mole % pyridine) at 1 lb/bbl. treat rate.Into one of these was added an additional 1 lb/bbl. of sodium styrenesulfonate. And into the other was added Zinc-Sulfo EPDM (10 milliequiv.Zinc (II)) at a 1 lb/bbl. treat rate. The mud was then measured intoaliquots and aged at 150° F., 300° F. and 400° F. for 16 hours inpressurized mud cells. The cells were then cooled to room temperatureand then rheological properties of the mud were measured on a Fann Model35 viscometer at 115° F. The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    The use of the polymer complex as an oil mud viscosifier is shown             in its inclusion in an OILFAZE MUD SYSTEM (Dresser Magcobar Inc.)                                    1# SPS/                                                                            1# ZnEPDM/                                        Temp(F.)                                                                           Rheology                                                                           (Control)                                                                          1# SPS                                                                            2# SPS                                                                            1# PSVP                                                                            1# PSVP                                           __________________________________________________________________________    150  AV   36   45  40  37   79                                                     PV   23   31  25  24   44                                                     YP   26   28  30  37   70                                                     ES   580  560 600 560  2000+                                             300  AV   36   41  64  52   93                                                     PV   27   30  40  33   55                                                     YP   18   22  48  38   76                                                     ES   240  320 400 400  380                                               400  AV   36   40  43  42   50                                                     PV   26   30  31  32   34                                                     YP   10   20  24  20   32                                                     ES   120  500 520 540  560                                               __________________________________________________________________________

What is claimed is:
 1. An oil-based drilling mud which comprises:(a) ahydrocarbon liquid substantially immiscible in water; (b) about 1 toabout 10 parts by weight of water per 100 parts by weight of thehydrocarbon liquid; (c) about 20 to about 50 lb/bbl. of at least oneemulsifier; (d) weighting material necessary to achieve the desireddensity; and (e) about 0.25 to about 4.0 lb/bbl. of a water insoluble,hydrocarbon soluble polymeric complex formed from a sulfonated polymerand a water insoluble vinyl pyridine polymer, wherein said vinylpyridine has a number average molecular weight of about 1,000 to about10,000 wherein said sulfonated polymer is an unneutralized orneutralized sulfonated polymer which has about 10 to about 200 meq. ofpendant unneutralized SO₃ H groups per 100 grams of polymer and has anumber average molecular weight of about 1,000 to 10,000 and said SO₃ Hgroups are neutralized with an ammonium or metal counterion, a molarratio of said sulfonated polymer to said vinyl pyridine being about 0.1to about
 20. 2. A process according to claim 1 wherein said metalcounterion is selected from the group consisting of antimony, tin, leador Groups IA, IIA, IB and IIB of the Periodic Table of Elements.
 3. Amud according to claim 1 wherein said SO₃ H groups are at least 90 molepercent neutralized.
 4. A mud according to claim 1 wherein saidneutralized sulfonated polymer is formed from an elastoeric polymer. 5.A mud according to claim 4 wherein said elastomeric polymer is selectedfrom the group consisting of EPDM termpolymer and butyl rubber.
 6. Adrilling mud according to claim 1 wherein said weighting material isbarite or barium sulfate.
 7. A drilling mud according to claim 1 whereinthe concentration level of said weighting material is sufficient to givesaid drilling mud a specific gravity of about 7 pounds per gallon toabout 20 pounds per gallon.
 8. A drilling mud according to claim 1wherein said hydrocarbon liquid is an oil.
 9. A drilling mud accordingto claim 1 wherein said hydrocarbon liquid is a hydrocarbon solvent. 10.A drilling mud according to claim 1 wherein said emulsifier is amagnesium or calcium soap of a fatty acid.
 11. A drilling mud accordingto claim 1 wherein said water is salt water.
 12. A drilling mudaccording to claim 1 wherein the concentration of said water is about 3to about 5 parts by weight per 100 parts by weight of said hydrocarbonliquid.
 13. A drilling mud according to claim 1 wherein said hydrocarbonliquid is a diesel oil.